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FOCUS ON RESEARCH The Case of the Disembodied Woman

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FOCUS ON RESEARCH The Case of the Disembodied Woman
67
The Central Nervous System: Making Sense of the World
Central sulcus
Frontal lobe
JAW
K
HIP
TRUN
E
KNE
ANKLE
EYEB
ALL
VO
CA
LIZ
AT
ION
IVA
TIO
N
WIN
EYE
NOS
E
Left
hemisphere
G
SWA
Motor areas (end view)
FIGURE
IND
TOES
LLO
NG
TO
WIN
G
UE
B
CHE
HEAD
SHOULDER
ARM
ELBOW
RM
FOREA
T
WRIS
SAL
Parietal lobe
D
HAN
TLE
LIT G
RIN DLE
D
MI
LIPS
ELBOW
FACE
UM
SHOULDER
NE
CK
BRO
W
EYEL
ID A
ND
WRIST
HAND
LE
LITT
G
RIN LE
D
MID EX
IND
TH
Somatosensory cortex
2.11
Motor and Somatosensory Cortex
The areas of cortex that move parts of the
body (motor cortex) and receive sensory
input from body parts (somatosensory
cortex) appear in both hemispheres of the
brain. Here we show cross-sections of only
those on the left side, looking from the
back of the brain toward the front. Areas
controlling movement of neighboring
parts of the body, such as the foot and leg,
occupy neighboring parts of the motor
cortex. Areas receiving input from neighboring body parts, such as the lips and
tongue, are near one another in the sensory cortex. Notice that the size of these
areas is uneven; the larger the area
devoted to each body part, the larger that
body part appears on the “homunculus.”
NECK
TRUNK
HIP
Motor cortex
TH EX
UM
B
LEG
FOOT
TOES
GENITALIA
Left
hemisphere
FACE
UPPER LI
P
LIPS
Corpus
callosum
LOWER LIP
W
AND JA
GUMS,
TEETH,
E
U
L
G
TON YNX
INA
OM
R
BD
PHA
A
RA
INT
Corpus
callosum
Sensory areas (end view)
Note: Did you notice the error in this classic drawing? (The figure shows the right side of the body, but
the left hand and left side of the face.)
Source: Penfield & Rasmussen (1968).
In fact, the actual process is quite complex. Recall again your sleepy reach for the coffee pot. To grasp its handle, your cortex must first translate the pot’s location into a
position relative to your body—to your left or right, for example. Next, the cortex must
determine which muscles must be contracted to produce the desired movement toward
that exact position. Groups of neurons work together to produce just the right combinations of direction and force in particular muscle groups. Making these determinations involves many interconnected areas of the cortex. Computer models of neural
networks are showing how these complex problem-solving processes might occur
(Graziano, Taylor, & Moore, 2002; Krauzlis, 2002).
FOCUS ON RESEARCH
Neurologist Oliver Sacks described the case of
“Christina,” a woman who had somehow lost
The Case of the Disembodied
the ability to feel the position of her own body
(Sacks, 1985). This case study led to imporWoman
tant insights about biological psychology that
could not be studied through controlled
experiments. It showed, for example, that the sense known as kinesthesia (pronounced
“kin-es-THEE-see-uh”) not only tells us where our body parts are but also plays an
important role in our sense of self.
Christina was a healthy young woman who entered a hospital in preparation for some
minor surgery. Before the surgery could be performed, however, she began to have difficulty holding onto objects. Then she had trouble moving. She would rise from bed and
flop onto the floor like a rag doll. Christina seemed to have “lost” her body. She felt
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